comm: prototype for task status updating
tasks: status-update
consts: new code for item_updated

Also renamed Change to Update
comm: send 'update task' message
tasks: ts_update_item_state_by_id
comm: implemented receiving of ITEM_UPDATED messages
comm: check scope for item_updated
js: fixed asserts for updateInfo event
js: implemented updating task status (untested)
js: doGetOneList: assertion; updated assert func
js: typo
js:duUpdateTaskStatus: improved task obj (still not working)
js: queryTasks: added "content-type" header

Without it Google will fail to parse our data.
js: doUpdateTaskStatus: removed thingsbreaking "var"
comm: remove "updating" msg after updating task status

This fixes #12 (well, at least must fix it).
Merge branch 'bug12_marktasks'

This implements marking tasks as done/undone. This is performed real-time
to Google servers, so may be not very fast.